MAINTAINERS: update bt8xx gpio F: patterns

Commit c103de2 ("gpio: reorganize drivers") renamed the file, update
the pattern.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Michael Buesch <m@bues.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -1618,7 +1618,7 @@ BT8XXGPIO DRIVER
 M:	Michael Buesch <m@bues.ch>
 W:	http://bu3sch.de/btgpio.php
 S:	Maintained
-F:	drivers/gpio/bt8xxgpio.c
+F:	drivers/gpio/gpio-bt8xx.c
 
 BTRFS FILE SYSTEM
 M:	Chris Mason <chris.mason@oracle.com>